Piston



Patented June 15, i943 STT E PESTON Original application March 7, 1940,Serial No.- 322,790. Divided and this application January 10, 1941,Serial No. 374,005

17 Claims.

This invention relates to improvements in pistons for liuid pressureproducing devices.

This application is a division of my pending application, SeriallNo.'322,790, viiled March '7,

1940, and is made in accordance with the United States Patent Oice RuleNo. 42. n

The invention is shown as embodied in a high pressure piston in a i'luldpressure producing device of the two phase type, as, for example, themaster cylinder in hydraulic brake mechanism. The piston embodying theinvention is constructed lto produce an effective seal within the highpressure chamber, and, further,it separates the high pressure chamberwithin the cylinder from the low pressure chamber therein and alsopermits iiow of liquid under pressure from the low pressure chamber intothe high pressure chamber.

An object of the invention is to provide a piston constructed towithstand high pressures and to effectively seal in a chambercomplementary thereto. l

One object of the invention is the provision of a piston having improvedmeans on its head yieldable under high pressure to eiectively inhibitthe passage of iiuid past the piston.

Another object of the invention is to provide a piston having ayieldable washer on its head, a pressure block thereon, and a sealingcup on the block effective under high pressure to cooperate and form aneffective seal.

Another object of the invention is to provide a piston, including a headhaving thereon' a rubber washer of high durometer reading, a pressureblock having a convex face seated upon a complementary face on thewasher, and a flexible sealing cup on the pressure block operative tofunction as a unit to establish an effective high pressure seal.

Other objects and advantages of the invention lwill appear from thefollowing description taken in connection with the accompanying drawingFig. 6 is an enlarged sectional view of the high pressure pistonillustrated in Figs. 1 and 2.

Referring to the drawing for more specific details of the constructionin which the invention is embodied, there is a single casting includinga reservoir i0 having a filling opening i2 normally closed-as by a headi4 having openingsi therethrough for venting the reservoir to theatmosphere, and a cylinder i3 at the base of the reservoir having one ofits ends closed as by a head 20 provided with a discharge port, 22 andits other end open. 1n the open end of the cylinder is a chamber 24 ofstandard gauge, bearingized, and provided with spa-ced ports 2t and 28affording communications between the chamber 24 and the reservoir iii.The cylinder i3 also has a bore 30, preferably of slightly less diameterthan the chamber 24 arranged forward of, concentric to, and in directcommunication with the chamber 24 and also with the discharge port 22.

A cylinder section 32 fitted tightly and sealed in the bore 30 has a.bearingized chamber and a circumierentially reduced portion providing inconjunction with the wall deiningfthe bore 30 an annular passage 36communicating with the chamber 24, and a port 38 arranged in the wall ofthe cylinder 32 provides a communication between the chamber 34 and theannular passage 36.

A piston 40 reciprocable in the chamber 24 is retained againstdisplacement by a washer 42 seated on the annular shoulder in the openend of the cylinder I8 and held in place by a retaining "ing 44 seatedin a groove in the wall of the cylinder. The piston 40 includes a head46, a body' 48 having a reduced diameter providing in conjunction withthe wall of the cylinder I8 an annular chamber 50 communicating with thereservoir ill as by way of the port 26, and a skirt 52 supporting asealing cup 54 for inhibiting seepage of uid from the annular chamber 50past the piston. The head 46 has a plurality of spaced passages 56therethrough providing communications between the annular chamber 50 andthat portion of the chamber 24 forward of the piston, and a sealing cup58 seated on the head 46 of the piston controls the passages 56.

A washer 60 seated on the end of the cylinder 32 opposite the piston 40has in its periphery a plurality of spaced notches 62 for the passage offluid between the chamber 24 and the annular of the washer, and a spring66 interposed be- .y

tween the sealing cup 58 and the washer 60 serves to retain the cup andwasher against displacement and also to assist in return of the piston40 to its retracted position.

The piston 40 has disposed concentrically in its body 48 a valve chamber68 opening through the head of the piston. This valve chamber has a port10 providing a communication between the valve chamber and the annularchamber 50, and also a vent 12 opening from adjacent the bottom of thevalve chamber into the annular chamber 50 for inhibiting fluid lock. Avalve 14 slidable in the valve chamber abuts a compression spring 16 ofhigh elasticity seated on the bottom of the valve chamber.

.The valve includes a cylindrical body 18 fitted snugly forreciprocation in the valve chamber. 'Ihis cylindrical body has aperipheral groove or slot 80 adapted to register with the port 10 in thevalve chamber so as to provide for passage of fluid from the chamber 24through the valve and into the annular chamber 50. The groove or slot 80is preferably tapered or calibrated so that uid may be metered graduallyfrom the'chamber 24 through the valve into the annular passage 50.

The valve 14 has a stem 82 formed integral with a piston 84 reciprocablein the chamber 34. The piston normally seats on the lands 64- of thewasher 60, It is essential that this piston be of such structure as towithstand high pressures without seepage of fluid past the piston andalso without injury to the component parts of the piston. The inventionherein claimed relates to this particular piston and the structureheretofore described constitutes in part the environment within whichthis piston functions.

As shown, this piston 84 includes a head 86 having a plurality ofpassages 88 therethrough providing communications between the chambers24 and 34, and a concentrically disposed shallow bore 90, A rubberwasher 92 seated on the head 86 of the piston has a concentric openingtherethrough registering with theshallow bore 90. 'I'his washer ispreferably constructed from rubber having a high durometer reading. Thediameter of the washer is slightly less than the gauge of the chamber34, so that uid may by-pass the washer when it is not under pressure.The washer 92 has a concaved face 94, and this concaved face inconjunction with the perimeter of the washer provided a pronounced lip96. A spacer or pressure block 08 seated .on

the concaved face of the washer has a convex face complementary to theconcaved face of the washer. The pressure block 98 has an extension |02concentrically disposed on its convexed face, and this extension isreceived by the opening in the Washer and also by the bore 90 in thehead of the piston with small clearance between lthe bottom of the boreand the free end of the extension |02, so as to limit thecompressibility of the washer and thus avoid binding of the washer inthe chamber 34.

The pressure block 88 has a plurality of spaced passages |04therethrough controlled as by a sealing cup |06 seated on the pressureblock. High pressure imposed on the sealing cup |00 is transmittedthrough the pressure block 98 to the washer 82.' This results in radialexpansion of the rubber washer 82, and, because of the particularcontour thereof, the lip 98, when the washer is 'deformed underpressure, engages the wall of the chamber with substantial bearingsurface.

'111e iuid pressure device within which the piston. 84 functionsincludes a two-way valve |88 seated within the head oi' the cylinder I8within the chamber 34 and controlling the discharge port 22. A spring||0 interposed between the sealing cup |06 and the two-way valve |08serves to retain the cup and valve against displacement and also toreturn the pistons 40 and 84 to their retracted positions. The spring||0 is of high elasticity, and is preferably balanced with the spring 16in the valve chamber 68.

A iiuid pressure delivery pipe or conduit ||2 has branches connectedrespectively to iluid pressure actuated motors ||4, preferably arrangedin pairs, one pair for actuating the brakes associated with the frontwheels of a vehicle, and another pair associated with the rear wheels ofthe vehicle.

The brakes may be of any preferred type. As shown, each of the brakesincludes a xed support or backing plate |l6, a rotatable drum H8associated therewith, a pair of friction elements or shoes |20 pivotedon the backing plate for cooperation with the drum, a retractile spring|22 connecting the shoes, anda motor corresponding to the fluid pressuremotors 4 mounted on the backing plate ||6 between the shoes andconnected thereto for actuating the shoes into engagement with the drumagainst the resistance of the retractile spring.

A thrust pin |24 has one of its ends seated in a socket in the back ofthe piston 40, and on the other end of the thrust pin is a coupling |26connected by a flexible boot |28 to the open end of the cylinder I8 forthe exclusion of dust and other foreign substances, A rod |30 has oneoi' its ends connected to the coupling |26 and its other end pivotallyconnected to a foot pedal lever |32 rockable on a stub shaft |34 andconnected by a retractile spring |36 to a xed support |38.

In a normal operation of the fluid pressure lbraking system, upondepressing the foot pedal lever |32 force is transmitted therefromthrough the rod |30 and thrust pin |24 to the piston 48. resulting inmovement of the piston'40 on its compression stroke, and also advancingthe piston 84.

During the initial movement of the pistons 40 and 84 on the compressionstroke, the sealing cup 58 on the piston 40 closes the port 28, and thesealing cup |06 on the piston 84 closes the port 38; and, thereafter, asthe pistons advance, iluid in the chamber 24 is displaced therefromthrough the passages 88 in the piston 84, past the the discharge port 22and fluid pressure delivery pipes ||2, into the iiuid pressure actuatedmotors H4, causing energization of the motors with the resultantactuation of the friction elements |20, into engagement with the drums||0 against the resistance of the retractile springs |22 to effectivelyretard rotation of the drums. During this operation, a large volume offluid is displaced from the chamber 24 at a comparatively low pressureto accomplish a quick vmovement of the friction elements into engagementwith the drums, and, thereafter, as the pistons advance, the reactionforce on the uid in the system forward of the pistons increases thepressure on the fluid in the chambers 24 and 34 until a predeterminedequalized pressure on the fluid in the chambersis attained. From thisperiod of operation, further advance of the pistons opposed by thereaction forces produces a, differential vof pressure in the chambers 24and 34, imposing a slightly greater pressure on the piston 84, tendingto hold the piston 84 against movement; and, thereafter, relativemovement of the pistons 40 and 84 gradually compresses thespring 16,resulting in cracking the valve and the metering of fluid by the valvefrom the chamber 24, through the calibrated passage 80 and the port 70into the annular chamber 50, thence through the port 26 into thereservoir. vThe passage 80 is so calibrated that the relief of iluid inthe chamber 24 is elected gradually so as to smooth out the operation.

In instances where the foot pedal lever |32 is actuated impulsively,resulting in an extremely rapid advance of the piston 40, pressurecreated on the fluid in the chamber 24 causes a rapid forward surge offluid in the chamber 24 against the back of the piston 34, tending toadvance the piston 84. This advance movement of the piston 84 isyieldingly resisted by the column of fluid in the system forward of thepiston 84 under the load of the friction elements of the respectivebrake structures.

The spring also yieldingly resists this movement of the piston 84. Thisspring is of high elasticity, hence the combined :reaction forcesinhibit material movement of the piston 84, and this results in flow offluid from the chamber 24 through the passages 88 in the piston 84, pastthe washer 92, through the passages |04 in the pressure block 98, andpast the sealing c up |06 into the chamber 34, until the pressures onthe fluid in the chambers 24 and 34 are equalized at a predeterminedpressure adequate to move the friction elements into engagement with thedrums, and, thereafter, as the pressure on the fluid increases, thereaction forces on the piston 84 open the valve 14 against theresistance of the spring 16, as in a normal operation.

Upon conclusion of a braking operation, the foot pedal lever |32 isreleased, and returns to its retracted position under the influence ofthe retractile spring |36. This results in retraction of the rod |30 andthrust pin |24, and release of the piston 40 and return of the pistons40 and 04 under the influence of the springs 66 and H0. During thisoperation, the spring 16 moves the valve 14 to its closed position.

As the pistons 40 and 84 return to their re- -traeted positions, apartial vacuum is created in the chamber 34, and this results in drawinguid from the reservoir I0 through the supply port 25, into the annularpassage 50, thence through the passages 56 in the head of the piston 40,past the sealing cup 58 thereon, into the chamber 24, thence through thepassages 88 in the pistonl 84, past the washer 82, through the lpassages|04 in the pressure block 98, and past the sealing cup |06 thereon intothe champer 34, completely filling the chambers 24 and 34.

During this operation, fluid is returning to the chamber 34 from thefluid pressure actuated motors ||4, and the fluid pressure deliverypipes connecting the motors to the `cylinder I8 under the influence ofthe retractile springs |22 connecting the friction elements of therespective brake structures. This may result in the chamber 34 receivinga quantity of fluid in excess of its-capacity, and under this condition,the ex- 38 and passage 36 into the chamber 24, thence through the port28 into the reservoir.

A modification of the invention is illustrated in Fig. 4. In thismodification the piston |40 has a head |42 provided with spaced passages|44' therethrough aiording communications between chambers |46 and |48.The head also has a concentric bore |50, and seated in the bore is aspring |52?,` A resilient washer |54 seated on the head has a marginallip |56 and a concentric opening |58 registering with the bore |50. Thiswasher is preferably made of rubber, having a high durometer reading,and the diameter of the Washer is slightly less than the gauge of thecomplementary chamber, so that fluid may normally by-pass the washer.

A spacer or pressure block |60 seated on the washer |54 has a facecomplementary to the face of the washer and a concentric extension |62received by the opening |58 in the Washer and the bore |50 in the headof the piston, and seated on the spring |52 so as to limit thecompressibility of the Washer to avoid binding thereof in thecomplementary chamber. The compression block has spaced passages |64therethrough for the passage of fluid, and seated on the pressure blockis a sealing cup |66 for control of the passages through the piston andthe pressure block.

As in the preferred embodiment of the invention, high pressure imposedon the sealing cup |66 is transmitted by the pressure block, |60 to thewasher |54, resulting in radial expansion of the Washer. Due to thecorresponding abutting faces of the washer and the pressure block, themarginal flange or lip |56 of the Washer is deformed under pressure andforced into engagement with the wall of the chamber over a subcessivequantity of fluid received by the chamber 34 `is displaced therefromthrough the port LTA device of the class described comprising a piston,an elastic member' thereon expansible radially, means cooperating withthe piston and responsive to fluid pressure to move relative to thepiston for compressing the elastic member and providing for the radialexpansion thereof, and sealing means supported on the elastic member.

2. A device of the class described comprising a piston, a compressiblemember thereon having a high durometer reading, a lfluid pressureresponsive block on the resilient member,and a sealing cup on thepressure block having a relatively low durometer reading and means inthe'plston resisting and limiting the movement of the pressure block.

3. A device of the class described comprising a piston, a compressiblemember thereon, a pres sure block on the compressible member, 'means forlimiting movement of the pressure block, and a sealing cup on thepressure block.

4. A device of the class described comprising a piston, a yieldablemember thereon having a concaved face, a pressure block seated in theconcaved face, said block responsive to fluidpresl-V sure means forlimiting movement of the pressure block, and a free oating sealing cupon the pressure block. A

5. A device of the class described comprising a piston, a radiallyexpansible Washer on the piston having a concaved face, a iiuid pressureresponsive block seated in the Washer having a convexface complementaryto the concave face of the washer, means for limiting movement of thepressure block, and a exibie sealing cup on the pressure block.

6. A device of the class described comprising a cylinder element, apiston reciprocable Within the cylinder having spaced passagestherethrough, a radially expansible washer seated on the piston of lessdiameter than the cylinder bore, said washer having a concaved face, apressure block seated on the concave face of the washer having aconvexed face complementary to the concaved face of the Washerresponsive to fluid pressure, means for limiting movementl of thepressure block, and a exible sealing cup seated on the pressure block.

'7. A device of the class described comprising a cylinder, a pistonreciprocable Within the yiinder, said piston having spaced passagestherethrough and a concentric recess, an elastic washer on the pistonhaving less diameter than the piston, said washer having a concaved faceand a concentric opening registering with the recess, a pressure blockhaving a convexed face complementary to and received by the -concavedface on the washer, an extension on thel convexed face of the pressureblock received through the opening in the washer and within the recessin the piston for limited relative movement between the piston and theblock, and a sealing cup on the pressure block.

8. A .device of the class described comprising a piston having spacedpassages therethrough and a concentric recess, an elastic Washer on thepiston having an opening therethrough registering with the recess, apressure block on the washer havingan extension received by the openingin the washer and the recess in the piston, a compression elementbetween the extension and the bottom of the recess, and a sealing cup onthe pressure block.

9. A device of the class described comprising a cylinder, a pistonreciprocable Within thecylinder and providing by-pass clearance with thecylinder wall, a radially expansible Washer seated against the head ofthe piston and normally providing by-pass clearance with the cylinderwall, a fluid pressure responsive member seated against the washeradapted to expand the washer radially when urged axially thereagainst,and a sealing member seated against the pressure member.

10. A device of the class described comprising a cylinder, a pistonreciprocable Within the cylinder and providing by-pass clearance withthe cylinder wall, a radially expansible washer seated against the headof the piston and normally clearing the cylindrical Wall throughout itscircumference and having a dished outer face, a pressure member seatedagainst the dished face of the washer and having by-pass clearance withthe cylinder wall and adapted to expand the Washer radially when urgedaxially thereagainst,

means limiting the compression of the washer by the pressure member, anda sealing member seated against the pressure member.

11. A device of the class described comprising a cylinder, a pistonreciprocable therein and having a by-pass clearance with the cylinderwall, a washer seating against the head of the piston and having anormal diameter spaced from the cylinder wall, said washer beingradially expansible under axial pressure to seal against the cylinderWall, and pressure sealing means seating against said washer having aportion normally sealing against the cylinder Wall, said sealing meansadapted to exert axial pressure on the washer to expand the sameradially into sealing engagement with the cylinder wall.

12. A device of the class described comprising a cylinder, a pistonreciprocable therein and having a by-pass clearance with the cylinderWall, a washer seating against the head of the piston and having anormal diameter spaced from the cylinder wall, said washer beingradially expansible-under axial pressure to seal against the cylinderwall, a pressure member seated against said Washer having a partextending therethrough toward the piston adapted to limit thecompressibility of the washer, and a sealing cup seated against saidpressure member normally sealing against the cylinder wall, and meansyieldingly urging said sealing cup pressure member and Washer toward thehead of the piston.

13. A device ofthe class described comprising a piston, an elasticmember thereon expansible radially, a pressure member'on the elasticmember and a sealing member on the pressure member, said members beingfree floating with respect to the piston and to one another.

14. A device of the class described, comprising a piston, a yieldablemember thereon, means limiting the yieldability of the member and asealing member supported on the means, said means and members being freeoating.

15. A device of the class described comprising a piston, a compressiblemember thereon expansible radially, a pressure block on the membersolely axially movable' relative n to the piston having a sealing meansassociated'J therewith, said sealing means responsive to fluid pressureto actuate the pressure block and thereby compress and provide forradial expansion of. the member, and means in the piston affordingresistance to movement of the block.

16. A device of the class described comprising a piston, an elastic`member thereon expansible radially thereto, a fluid pressure responsiveblock juxtaposed on the member and supported by the piston for axialmovement relative thereto, and a sealing cup on the pressure blockmovable axially relative to the piston and expansible radially relativethereto, the block effective upon movement relative to the piston tocompress the central portion of the elastic member and provide foruniform radial expansion thereof.

17. A device of the class described comprising a piston, an elasticmember on the head thereof a fluid pressure responsive block juxtaposedon the member and supported by the piston for axial movement relativethereto, the block effective upon movement toward the piston to compressthe elastic member therebetween and provide for peripheral expansion ofthe elastic member, and a sealing means on the block.

OWEN H. FOWLER.

